In late years, video cameras, single-lens reflex cameras and mirrorless cameras that are configured to take both motion pictures and still images (simply “the cameras” hereinafter) are spreading.
Generally, in such a camera, a diaphragm value is changed (adjusted) in a camera body. But, in some cameras, a lens barrel is provided with a diaphragm ring, and the diaphragm value is changed by turning the diaphragm ring (for instance, see Patent related document 1).
FIG. 7 is a plan view that shows an instance of a conventional structure of a lens barrel with diaphragm adjustment mechanism, and a reference number 100 in the figure denotes a lens barrel, a reference number 104 denotes a diaphragm ring being free to be rotated, and a reference number 105 denotes a focus ring. Such a diaphragm ring 104 is provided with a click mechanism (not shown) that is configured to fix the diaphragm ring 104 at a predetermined diaphragm value, F-value, such as F1.4, F2, F2.8 . . . so as to restrict its free rotation.
When taking a still image with such a camera, the diaphragm value is set in advance, taking brightness of a subject into consideration. In some cases, when taking a motion picture, the change of the diaphragm value is desired without fixing during taking it. For instance, in a case where a motion picture is obtained in a moving helicopter or on a car, or a motion picture is obtained, putting the cameral on a radio control helicopter, brightness of a subject may be widely changed, and a diaphragm value may be needed to be changed in order, depending on the brightness of a subject. In such a case, the above-mentioned click mechanism may obstruct a smooth rotation of the diaphragm ring 104, and a microphone of the camera may catch click sounds.
Then, the lens barrel for solving such problems has been proposed (for instance, see Patent related document 2).
FIG. 8(a) is a cross sectional view that shows another instance of the lens barrel with diaphragm adjustment mechanism having a conventional configuration, and FIG. 8(b) is its enlarged sectional view. A reference number 204 in the figure denotes a diaphragm ring, a reference number 206 is a click mechanism, a reference number 206A denotes a spring that is a component of the click mechanism 206, and a reference number 206B denotes a click ball that is energized through the spring 206A. And, a reference number 206C denotes an engaged portion with which the click ball 206B is able to be engaged, and a reference number 207 denotes an annular member which end surface has two or more engaged portions 206C. Such a annular member 207 is configured to be freely rotated, such that a contact between the click ball 206B and the engaged portion 206C is released when the annular member 207 is 180° rotated, and the click mechanism stops.